Desulphurization of hydrocarbon oils



8, 1 R. D. BENT ETAL 22 DESULFHURIZATION 0F HYDROCARBON OILS Filed A rii15, 1941 Inventors G263 Charles A. Pines M T By M a aw I Their AflmrneyPatented Feb. 8, i944 2,340,922 DESULPHURIZATIgfigF HYDROCARBON RobertD. Bent, Springfield, and Charles A. Pines, Upper. Darby, Pa., asslgnorsto The Atlantic Refining Company, Philadelphia, Pa., a corporation ofPennsylvania Application April 15, 1941, Serial No. 388,570

8 Claims.

The present invention relates to the treatment of hydrocarbon oils, andmore particularly to the production of gasoline of improved leadsusceptibility and reduction in sulphur content of .higher boiling oilcomponents. a

An object of this invention is the desulphuriza- 'tion of hydrocarbonmixtures, and particularly the catalytic desulphurization of hydrocarbonoils containing high boiling components, which, per se, aresubstantially unvaporizable at desulphurizing temperatures.

A further object of this invention is the desulphurization of relativelylong boiling range petroleum distillates obtained by the straight-rundistillation of crude petroleum, and comprising hydrocarbons boilingfrom 100 F. to 800 F. Such long boiling range distillate includes thehydrocarbons normally separated by fractifination into gasoline,kerosene, furnace oil, and gas oil.

A further object of this invention is the vapor phase desulphurizationof a relatively long boiling I range distillate in the presence of adesulphurization catalyst, particularly fullers earth, at temperaturesbetween 600 F. and 800 F., followed by the separation of the treateddistillate into fractions, and the further treatment of a gasolinefraction to improve the lead susceptibility thereof. It has beenproposed heretofore to desulphurize gasoline distillates by treatmentin" the vapor phase with catalysts such as fullers earth or bauxite attemperatures of the order of 600 F. to 800 F. However, when this processof catalytic desulphurization was applied to higher boiling distillates,such as gas oil, considerable difilculty was encountered due to the factthat the higher boiling distillates could not be vaporized withoutdecomposition at the temperature required for desulphurization, and as aresult, the products of decomposition, particularly tarry matter andcarbon, were deposited on the catalyst, thus reducing the useful life ofthe catalyst so greatly that the process became impractical. In ourcopending application Serial No. 386,972 we have disclosed a methodwhereby the above mentioned difllculties may be obviated, and that wewere able to obtain substantial desulphurization of higher boilinghydrocarbon distillates without decomposition'by treating a relativelylong boiling rangedistillate containing said higher boilinghydrocarbons. More particularly, we have disclosed that high boilinghydrocarbons may be catalytically desulphurized in the vapor phase byhaving present a quantity of lower boiling hydrocarbons suflicient topermit vaporization of the higher boiling hydrocarbons withoutsubstantial decomposition at the desulphurization temperature. In theevent that the lower boiling hydrocarbons, such as gasoline, likewisecontained sulphur compounds which it was desirable to remove,such lowerboiling hydrocarbons were desulphurized simultaneously with the higherboiling hydrocarbons.

However, we have found that while we were able to obtain simultantouslysubstantial desulphurization of both the gasoline and the higher boilinghydrocarbons in accordance with our process aforesaid, the leadsusceptibility of the gasoline was not s'uillciently high to permit itsuse in the production of extremely high octane motor fuel, for example,aviation gasoline. By lead susceptibility we means the ability of thegasoline to respond to the addition of tetraethyl lead, as reflected inthe increase in octane value. For example, two gasolines ofsubstantially the same physical properties but differing in chemicalcomposition or sulphur content may respond difierently to the additionof equal quantities of tetraethyl lead. In one case the addition of 3cc. of tetraethyl lead may increase the octane value by 5 or 6 units,whereas in the second case, the increase may be only of the order of 2to 3 units. In the manufacture of aviation gasoline of high octanevalue, for example, octane, where the quantity of tetraethyl leadpermissible is limited to 3 cc. per gallon, it becomes necessary toemploy, as a base, a gasoline of relatively high initial octane valueand preferably of high lead susceptibility. In accordance with thepresent invention we are able to produce not only gasoline of high leadsusceptibility but also substantial quantities of higher boilinghydrocarbons such as furnace oil and gas oil of reduced sulphur content.

In the practice of our invention, we produce a relatively long boilingrange distillate, for example, a mixture of hydrocarbons boiling withinthe range of from 100 F. to 800 F. and containing objectionable-sulphurcompounds, by distilling from crude petroleum the hydrocarbonsnorquantity really comprising gasoline, kerosene, furnace oil and gasoil. This hydrocarbon mixture is then vaporized by heating to atemperature oi from 608 F. to 800 F., preferably 750 F., the presence 01the lower boiling hydrocarbons, i. e., gasoline and kerosene, assistingin the vaporization of the higher boiling hydrocarbons, particularly gasoil, and thereby preventing substantial decomposition of the gas oil. Inthe absence of the lower boiling hydrocarbons, the gas oil is incapableof being vaporized except at temperatures above those desired fordesulphurization, and then only with excessive deccmpositionor cracking.The vaporized hydrocarbon mixture is thereafter brought into contactwith a desulfurizing catalyst, such as fullers earth, at a temperatureof from 600 F. to'800" R, and preferably at a temperature of from 700 F.to ?50 F., for a period of time sumcient to effect conversion of thesul-' phur compounds to lower mercaptans and Has without substantialdecomposition of the hydrocarbons. Pressures employed in thedesulphurizing operation may be atmospheric or superatmospheric, and wehave found that pressures of the order of 30 to 50 pounds per squareinch are quite suitable. The treated vapors, after removal from contactwith the catalyst, are then separated by fractionation into distillatesof desired boiling range, for example, gasoline, kerosene, furnace oil,and gas oil, and the mercaptans and ms thereafter removed from thedistiliates by conventional methods. The gasoline fraction, afterremoval of H28, isthen vaporized and contacted with a. desulphurizingcatalyst, such as fuliers earth, at a temperature between 600 F. and 800F., and preferably between 700" F. and 750 F., in order to dissociate orconvert residual sulphur compounds into dissociated, readily removablecompounds such as HzS, whereby the lead susceptibility of the gasolinefraction is markedly improved. In producing the relatively long boilingrange charging stock, it is preferable that such stock contain fromabout 20 per cent to about 80 per cent of hydrocarbons boiling withinthe gasoline boiling range, 1. e., from 100 F. to 400 F. However, wehave found that very satisfactory results may be obtained by using inaddition to the gasoline hydrocarbons, a suitable of hydrogen ornormally gaseous hydrocomprising, for example, on or a mix= ture of twoor more hydrocarbons containing from 1 to 4 carbon atoms per molecule.For instance, we may treat hydrocarbon mixtures comrising gasoline,kerosene, furnace oil, and gas oil to which have been added a suitablequantity of hydrogen or hydrocarbons of the nature of propane or butane,such added gas or gases comprising of the order of 5 per cent to 50 percent of the mixture. In the practice of our invention, we have foundthat not all of the diflicultly-removable sulphur compounds contained inthe charge oil are converted into HzS. For example, in many cases thesulphur compounds occurring in the higher boiling oil components arecon. verted into low molecular weight mercaptans such as methyl andethyl mercaptans, which appear as such in the gasoline fractionsseparated from the treated oil, and which may be removed by our secondstage treatment with a desulphurlzing catalyst. Insofar as thedesulphurizing catalysts are concerned, we prefer to employ fullersearth, for example, 30-60 mesh fullers earth which may or may not havebeen calcined by heating at temperatures of the order of 800 F. to 1100F. Other desulphurlzing catalysts such carbons,

assume as bauxite, brucite, acid activated bentonite, not ural orsynthetic silicates of aluminum, calcium, and magnesium, alumina-silicamixtures or complexes, metal oxides or sulphides, and the like may alsobe employed. These catalysts may be in the form of granules, of forexample, 4 to mesh, or may be in the form of pellets or tablets ofsuitable size. In many cases the desulphurizing emciency of thecatalysts may be enhanced bythe introduction of limited amounts of wateror steam into the hydrocarbon vapors hem charged to the catalyst bed.

Our invention may be further understood with reference to theaccompanying drawing which illustrates diagratically a system suitablefor carrying out our process.

Referring to the drawing, crude petroleum containing a substantialquantity of lower boiling hydrocarbons is delivered, under a pressure offor example, 140 pounds per square inch, by pump 6 through pipe 2 to thetubular heater 8, wherein the crude oii is heated to a temperature ofthe order of 750 F. As a result of the heating, a substantial proportionof the crude oil is vaporized and the mixture of vaporized andunvap'orized oil is passed by means of pipe t to evaporator tower 5,wherein the unvaporized residual oil is separated from the vaporized oilwhich comprises, for example, the hydrocarbons normally constitutinggasoline, kerosene, furnace oil, and gas oil. Such vaporizedhydrocarbons may represent, for example, from 50 per cent to 70 per centof the crude oil initially charged, and includes hydrocarbons andsulphur compounds boiling up to about 800 F. or slightly higher. A

suitable quantity of steam may be introduced into pipe l by means ofvalve-controlled pipe t, the

steam commingling with the hydrocarbon vapors passing through pipe d andlater serving to enhance the desulphurizing emciency of the catalyst.

The unvaporized residual oil may be withdrawn from the evaporator bymeans of valve-controlled pipe '5 and disposed of as desired, while thehydrocarbon vapors, and sulphur compounds, are passed from the top ofthe evaporator through pipe 8 and valve-controlled pipe 9 into catalystcasing I0 provided with a bed of catalyst l I, such as granular fullersearth. In passing downwardly through the catalyst bed H, at atemperature of, for example, 750 F., the sulphur compounds contained inthe hydrocarbon vapors are dissociated or converted into more easilyremovable compounds such as lower mercaptans and H23, withoutsubstantial decomposition of the hydrocarbons. The time of contact inthe catalyst bed may be of the order of 1 to 60 seconds, and contacttimes of about 30 to 40 seconds have been found very satisfactory. Asmall amount of hydrocarbon gas and hydrogen may be formed during theconversion step, but extensive cracking of the hydrocarbons does nottake place. The hydrocarbon vapors and H28 are drawn from the bottom ofcasing ID by means of valve-controlled pipe l2 and delivered by pipe l3to fractionating tower ll provided with heating coil l5 and bubble traysI6. When the desulphurizing activity of the catalyst in casing Illbecomes exhausted, such casing may be cut out,

of the system by closing valve-controlled pipes 0 and I2, and uponopening valve-controlled pipes l1 and I8, the second casing I9 providedwith catalyst bed 20 may be placed on stream. In this manner, continuousoperation may be maintained, the spent catalyst H being regenerated orreplaced while the catalyst bed 20 is in use. If desired, the catalystcasings may be operated in series, in which case three casings may beemployed, two on stream and one on stream, to maintain continuousoperation.

The treated hydrocarbon vapors and H28 introduced into fractionatingtower l4 are subjected to fractionation, whereby hydrocarbon fractionsof the desired boiling range are separated from one another. Forexample, gas oil may be withdrawn from the bottom of the tower throughvalve-controlled pipe 2|, a liquid side stream of furnace oil throughvalve-controlled pipe 22, and a liquid side stream of kerosene throughvalve-controlled pipe 23. All of these fractions may be subjected toconventional steam stripping, if desired, in order to remove traces ofhydrocarbons boiling aboveor below the desired range for the particularfraction. Hydrogen sulphide may be removed from the fractions, forexample, by washing with sodium hydroxide solution or equivalentreagent. The resulting fractions contained substantially less sulphurcompounds than similar fractions which had not been subjected totreatment in accordance with our invention.

From the top of tower [4 are withdrawn the vapors comprising the lowerboiling hydrocarbons, i. e., gasoline, admixed with hydrocarbon gasesand H25. This mixture is delivered by pipe 24 to condenser 25, thehydrocarbon vapors are condensed, and the condensate together with thehydrocarbon gases and HaS are introduced into separator 26, wherein thegasoline condensate is separated from the gases. The gasoline condensateis drawn from the bottom of separator 26 and a portion thereof returnedby valve-controlled pipe 21, pump 28, and pipe 29 to the top of tower I4to serve therein as reflux. The re-. mainder of the condensate is passedby means of valve-controlled pipe 30 to the lower section of drawn fromthe upper section of tower 31 and delivered by pump 40 and pipe 4| tothe tubular heater 42, wherein the gasoline is heated to a temperaturebetween 600 F. and 800 F., and

preferably between 700 F. and 750 F. The gascline is thus substantiallycompletely vaporized and the vapors are passed from the heater by meansof pipe 43 and valve-controlled pipe 44 into catalyst casing 45 provided.witha bed of catalyst 46, such as granular fullers earth. A suitablequantity of steam may be introduced into pipe 43 ,by means ofvalve-controlled pipe 41, the steam commingling with the gasoline vaporspassing through pipe 43 and later serving to enhance-the desulphurizingefiiciency of the catalyst. In passing downwardly through the catalystbed 46, at a temperature of, for example, 750 F., the residualundissociated sulphur oom- -p0unds contained in the gasoline vapors aredissociated or converted into more easily removable compounds such asHas, without substantial decomposition of the gasoline. The time ofcontact in the catalyst bed may be of the order of 1 to 60 seconds, andcontact times of about 5 to 20 seconds have been found-verysatisfactory. A small amount of hydrocarbon gas and hydrogen may beformed during the conversion step, but extensive cracking of thegasoline does not take place. The gasoline vapors and HaS are drawn fromthe bottom of casing 45 by means of valve-controlled pipe 48 anddelivered by pipe 49 to condenser 50,- wherein the vapors areconscrubbing tow'er 31 for treatment hereinafter described. Theuncondensed hydrocarbon gases and Has are withdrawn from the top ofseparator 26 and may be passed from the system through valve-controlledpipe-3|, or a portion of the gases may be passed by valve-controlledpipe 32 and pump 33 through H2S scrubber 34, and the Has-free gas thenrecycled by pipe 35 to pipe 2 for admixture with the crude oil chargedto tubular heater 3. Hydrocarbon gases or hydrogen supplied from anexternal source may be introduced into the oil charged to the system bymeans of valve-controlled pipe 36.

The gasoline condensate from separator 26 containing dissociated sulphurcompounds, i. e., H28, and residual undissociated sulphur compounds, ispassed upwardly through scrubbing tower 31 in intimate countercurrentcontact with a solution of an alkaline agent, for example, sodiumhydroxide, whereby the H28 is neutralized and removed from the gasoline.Fresh solution may be introduced into the top of tower 31 by means ofvalve=controlled pipe 38 and spent solution removed from the bottom ofthe tower by densed, and the condensate and H28 then passed from thesystem through valve-controlled pipe 5|. The gasoline condensate may betreated with an alkaline agent to remove H28, and a gasoin which casethree casings may be employed,

means of valve-controlled pipe 39. In lieu of the two on stream and oneoff stream, to maintain continuous operation,

The following example will serve to illustrate the results which may beobtained in accordance with our invention, and is not to be construed aslimiting the scope thereof.

A West Texas crude petroleum was heated in a pipe still to effectvaporization of a substantial proportion thereof, and the heatedvapor-liquid mixture was charged to an evaporator tower wherein thevapor was separated from the unvaporized residuum} The vapor from thisseparation, representing approximately 70 per cent of the crude charged,was then passed through a bed of fullers earth at 750 ,F. and about 25pounds per square inch pressure, and the treated vapors were thenfractionated into'a light naphtha fraction, a reformer stock (heavynaphtha), a furnace oil fraction, and heavy gas oil. The

light naphtha fraction was treated for the removal of dissociatedsulphur compounds, i. e.,

H25, and the treated naphtha was then vaporized and passed through asecond bed of fullers earth at a temperature of 750 F. under a pressureof 50 pounds per square inch to efiect dissociation of residual sulphurcompounds and to I improve the lead susceptibility of the naphtha. Thesulphur content of all of the product fractions was determined on anHzS-iree basis.

Crude oil Light as- 011 stock... twat? 6 A. P. I. gravity ..degrees.-36. Percent suliur l. 30 0. 044

0 ratin conditions:

Volur ne percent oil vaporized and charged to catalyst bed 69. 9 100. 0Volume charge per volume catalyst per hour 0. 547 l. 81 Temperature oicatalyst bed.. 2 .F.. 750 760 Pressure ....pounds per square mch.. 25 50Yield oi products, weight percent:

Light distillate Reformer stock Furnace 011..... Gas oil (heavResiduum.. Gas

Inspection oi products:

Light distlllate- A. P. I. gravity ..degrees.. Percent sulphurDistillation range F..

Reformer stock A. P. I. gravity ..degrees.. Percent sulphur Distillationrange ..I"..

Furnace oil A. P. I. gravity ..degrees..

Percent sulphur... Distillation range.

Gas 011 (heavy)- A. P. I. gravity ..degrees.. Percent sulphurDistillation range .F

Reslduum- A. P. I. gravity ..degrees.. Percent sulphur Percent sulphurin total liquid products Percent sul hur removal from crude Percent suphur removal from catalytically treated products 1 The light distillatewas that produced in the first run.

In the following/table are shown the relative lead susceptibilities of(1) untreated light naphthe. obtained by the straight-run distillationof the crude oil, (2) the treated light distillate from the first run,and (3) the treated light distillate From the above example, it will beseen that in accordance with our invention we are able to efiect asubstantial decrease in the sulphur content of both the lower boilingand higher boiling components of a relatively long boiling rangedistillate without substantial decomposition or cracking of thecomponents, and at the same time we have also obtained a substantialimprovement in the lead susceptibility of the light naphtha distillate.By our method it is therefore possible to accomplish not onlydesulphurization and improvernent in lead susceptibility of the lowerboiling hydrocarbons, but also desulphurization of high boilingcomponents which are otherwise not amenable to desulphurization, per se,without substantial decomposition, and by thus avoiding decomposition weare able to extend the life of the catalyst and render thedesulphurization-oi the higher boiling components commerciallypracticable.

What we claim is:

1. The method or treating hydrocarbon oil to produce gasoline ofimproved lead susceptibility and desulphurized higher boilingcomponents, which comprises separating from crude petroleum a longboiling range distillate containing gasoline components and higherboiling components which are substantially unvaporizable at atmosphericpressure without decomposition, contacting said distillate substantiallyin the vapor phase with a desulphurizing catalyst at a temperaturebetween 600 F. and 800 F. to dissociate the sulphur compounds containedin said distillate, separating from said distillate a gasoline tractioncontaining dissociated and undissociated sulphur compounds and afraction comprising higher boiling components having a reduced contentof sulphur compounds, removing from said gasoline fraction thedissociated sulphur compounds, and contacting said gasoline fractionsubstantially in the vapor phase with a desulphurizing catalyst at atemperature between 600 F. and 800 F. to dissociate residual sulphurcompounds and improve the lead susceptibility of said gasoline.

2. The method of treating hydrocarbon oil to produce gasoline ofimproved lead susceptibility.

and desulphurized higher boiling components, which comprises separatingfrom crude petroleum a long boiling range distillate containing highboiling components readily susceptible of decomposition by heating atthe normal vaporization temperature thereof and a quantity of gasolinecomponents suflicient to permit substantially complete vaporization ofthe high boiling components together with the gasoline components at atemperature between 600 F. and 800 F. without substantial decomposition,contacting said distillate substantially in the vapor phase with adesulphurizing catalyst at a temperature between 600 F. and 800 F. todissociate the sulphur compounds contained in said distillate,separating from said distillate a gasoline fraction containingdissociated and undissociated sulphur compounds and a fractioncomprising higher boiling components having a reduced content of sulphurcompounds, removing from said gasoline fraction the dissociated sulphurcompounds, and contacting said gasoline fraction substantially in thevapor phase with a desulphurizing catalyst at a a temperature between600 F. and 800 F. to dissociate residual sulphur compounds and improvethe lead susceptibility oil-said gasoline.

3. The method of treating hydrocarbon 011 to produce gasoline ofimproved lead susceptibility and desulphurized higher boilingcomponents, which comprises separating from crude petroleum a longboiling range distillate containing high boiling components readilysusceptible of decomposition by heating at the normal vaporizationtemperature thereof and a quantity of gasoline components sumcient topermit substantially complete vaporization of the high boilingcomponents' together with the gasoline components at a. temperaturebetween 700 F. and 750 F. without substantial decomposition, contactingsaid distillate substantially in the vapor phase with fuller's earth ata temperaturebetween 700 F. and 750 F. to dissociate the sulphurcompounds contained in said distillate, separating from said distillatea gasoline fraction containing dissociated and undissociated sulphurcompounds and a fraction comprising higher boiling components having areduced content of sulphur compounds, removing from said gasolinefraction the dissociated sulphur compounds, and contacting said gasolinefraction substantially in the vapor phase with fullers earth at atemperature between 700 F. and 750 F. to dissociate residual sulphurcompounds and improve the lead susceptibility of said gasoline.

4. The method of treating hydrocarbon oil to produce gasoline ofimproved lead susceptibility and desulphurized higher boilingcomponents, which comprises separating from crude petroleum a distillateboiling within the range of from 100 F. to 800 F. and containing highboiling, readily decomposable components, contacting said distillatesubstantially in the vapor phase with a desulphurizing catalyst at atemperature between 600 F. and 800 F. to dissociate the sulphurcompounds contained in said distillate. separating from said distillatea gasoline fraction containing dissociated and undissociated sulphurcompounds and a fraction comprising higher boiling components having. areduced content of sulphur compounds, removing from said gasolinefraction the dissociated sulphur compounds, and contacting said gasolinefraction substantially in the vapor phase with a desulphurizing catalystat a temperature between 600 F. and 800 F. to dissociate residualsulphurcompounds and improve the lead susceptibility of said gasoline. v

5. The method of treating hydrocarbon oil to produce gasoline ofimproved lead susceptibility and desulphurized higher boilingcomponents, which comprises separating from crude petroleum a longboiling range distillate comprising hydrocarbons up to and including gasoil, contacting said distillate substantially in the vapor phase with adesulphurizing catalyst at a temperature between 600 F. and 800 F. todissociate the sulphur compounds contained in said distillate,separating from said distillate a gasoline fraction containingdissociated and undissociated sulphur compounds and a higher boilingfraction having a reduced content of sulphur compounds, removing fromsaid gasoline fraction the dissociated sulphur compounds, and contactingsaid gasoline fraction substantially in the vapor phase with adesulphurizing catalyst at a temperature between 600 F. and 800 F. todissociate residualsulphur compounds and improve the lead susceptibilitytialiy in the vapor phase with a desulphurizing catalyst at atemperaturebetween 600 F. and 800 F. to dissociate the sulphur compoundscontained in said distillate, separating from the treated distillate aplurality of fractions at least one of which comprises gasolinecontaining dissociated and undissociated sulphur compounds,

removing from said gasoline fraction the dissociated sulphur compounds,and contacting said gasoline fraction substantially in the vapor phasewith a desulphurizingicatalyst at a temperature between 600 'F. and 800F. to dissociate residual sulphur compounds and improve the leadsusceptibility of said gasoline.

7. The method of treating hydrocarbon oil to produce gasoline ofimproved lead susceptibility and desulphurized higher boilingcomponents, which comprises separating from crude petroleum a distillatecomprising gasoline, kerosene, furnace oil, and gas oil, contacting saiddistillate substantially in the vapor phase with a desulphurizingcatalyst at a temperature between 700 F. and 750 F. to dissociate thesulphur compounds contained in said distillate, separating from thetreated distillate a plurality of fractions at least one ofwhichcomprises gasoline containing dissociated and undissociated sulphurcompounds, removing from said gasoline fraction the dissociated sulphurcompounds, and contacting said gasoline fraction substantially in thevapor phase with a desulphurizing catalyst at a temperature between 700F. and 750 F. to dissociate residual sulphur compounds and improve thelead susceptibility of said gasoline.

8. The method of treating hydrocarbon oil to produce gasoline ofimproved lead susceptibility and desulphurized higher boilingcomponents, which comprises separating from crude petroleum a distillatecomprising gasoline, kerosene, furnace oil, and gas oil, contacting saiddistillate substantially in the vapor phase with fullers earth at atemperature between 700 F. and 750 F. to dissociate the sulphurcompounds contained in said distillate, separating from the treateddistillate aplurality of fractions at least one of which comprisesgasoline containing dissociated and undissociated sulphur compounds,removing from said gasoline fraction the dissociated sulphur compounds,and contacting said gasoline fraction substantially in the vapor phasewith fullers earth at a temperature between 700 F. and 750 F. todissociate residual sulphur compounds and improve the leadsusceptibility of said gasoline.

\ ROBERT D. BENT.

CHARLES A. PINES.

